Changes in reflex connections caudal to spinal cord transection will be studied. We will make use of the technique of spike triggered averaging to measure the functional connections of singe spindle afferent fibers. We are interested in examining mechanisms by which increases in this Ia-motoneuron projection are achieved following either acute or chronic spinal cord transection. We also will make anatomical studies of the motoneurons to see how changes in soma size or dendritic fields might contribute to these changes. Frogs with grafted supernumerary hindlimbs will be studied to ascertain the location of motoneurons supplying muscles of the extra limb. Is functional capacity of the supernumerary limb related to the motoneurons being located appropriately? We are also interested in birth date analysis of dorsal root ganglion cells to see whether those supplying the supernumerary limb are "born" at the same time as neurons in the same ganglion which supply the normal structures of the frog.